1. Field of the Invention
The present invention relates to a technique for controlling the operation of a pump; and more particularly, the present invention relates to a method and apparatus for controlling the speed of a pump, e.g., for domestic and commercial heating or cooling water systems.
2. Brief Description of Related Art
Current techniques on variable speed pump controls for domestic and commercial heating or cooling water systems are based upon a proportional integral derivative (PID) control algorithm with respect to a system differential pressure verses a constant pressure set point. Some other control parameters may also include flow rate, power and so forth. A typical water heating or cooling hydronic system is shown below schematically in FIG. 1, including FIGS. 1a and 1b. The corresponding system curve and control curve for a balanced system are shown below schematically in FIG. 2. The constant set point control method that is currently used in the pump control system is very simple and has been applied successfully for cooling and heating water supply applications for many years.
The pump control community has recently noted, however, that quite an amount of operation energy required to run pumps by using this method is wasted due to the pressure point being set much higher than the actual system pressure needed actually to meet the flow requested at the time, which is indicated by the shaded area in FIG. 2 above.
Recently, issues regarding energy saving and environmental protection have been addressed dramatically and significantly. More attention has been paid to all control applications, includes pump controls for domestic and commercial heating or cooling water systems. In order to reduce energy consumption and operation costs, some innovations to the current pump control method may need to be made.